1. Field of the Invention
The invention relates to well components and in particular to a combination well piston and paraffin scraper which moves vertically within a well delivery tube to assist in bringing undesirable liquids and paraffin deposits to the top of the tube. More particularly, the invention relates to a gas well piston and paraffin scraper construction having rotor means which revolves during ascent of the piston within the delivery tube, creating a turbulence which forms a seal with the tube wall to increase the lift pressure on the piston.
2. Description of the Prior Art
A problem which exists in many gas and oil wells is the accumulation of paraffin deposits on the inner walls of the fluid delivery tube which restricts the flow of the fluid from the well if not removed. These paraffin deposits are particularly troublesome in gas wells. Many wells employ a free floating piston type scraper or "rabbit" which moves vertically within the delivery tube to scrape the paraffin from the tube walls. The lifting force for these scrapers is supplied by the pressure of the well gas as the gas is removed from the well for delivery into a pipeline or collection tanks.
Another common problem especially in low volume gas wells, is the removal of oil, water and other liquids which accumulate at the bottom of the well. These liquids, if not removed, restrict the gas flow requiring subsequent "blow-out" of the well, in which the well is opened to the atmosphere for a sufficient time period for the liquid to flow to the surface resulting in loss of usable gas.
Numerous types and arrangements of pistons and paraffin scrapers for wells have been devised for removal of such paraffin deposits and liquids. Examples of such constructions are shown in U.S. Pat. Nos. 1,720,049; 2,182,931; 2,184,393; 2,893,493; 3,034,581; 3,171,487; 3,229,768; 3,329,211; 3,394,763 and 3,456,727. These constructions use various blade arrangements and configurations for scraping the paraffin from the tube walls in combination with springs, discharge ports, sealing rings and other components to increase their efficiency. Most of these constructions are primarily concerned with removal of the paraffin with some having a secondary effect of removing the undesirable liquid accumulations from the bottom of the well.
Problems, however, occur in the use of many of these types of piston scrapers. The piston will rise rapidly within the tube upon initial opening of the gas delivery line but when used in a low volume, low pressure well, will stop in the tube before reaching the top thereof. Such stopping occurs because the gas pressure below the piston reaches the gas pressure above, due largely to escape of the propelling gas between the scraper elements and tube walls.
No gas well piston and paraffin scraper construction, of which we are aware, eliminates or reduces such problems by mounting a rotor element on the bottom of the piston which is believed to produce a turbulence in the spaced area between the rotor element and an adjacent wiper ring to effectively form a seal with the tube wall, thereby increasing the effective lift on the piston.